Pictures from the San Francisco Chronicle showed firefighters wearing oxygen masks as they entered the home on April 4. Authorities say the victim, believed to be about 90 years old, may have died five years ago. Foul play is not suspected. Her daughter apparently still lived in the home, hoarding the trash and hanging onto her mother.

Police called it the worst case of hoarding they've ever seen.

The mummified body of an elderly woman was discovered in a San Francisco home on April 4, 2015.

An expert says hoarding is a mental disorder where people who have suffered trauma hold onto things as security.

"Imagine someone is physically trying to rip your child from you and you say, 'No, this is my child.' That's the feelings and emotions that can be associated with this," said Mark Salazar of the Mental Health Association of San Francisco. "It's that strong."